A personal wireless area network (WPAN) is a network used for communication among computing devices (for example, personal devices such as telephones and personal digital assistants) close to one person. The reach of a WPAN may be for example a few meters. WPANs may be used for, e.g., interpersonal communication among personal devices themselves, or for connecting via an uplink to a higher level network, for example the Internet.
The IEEE 802.11 ad was formed in year 2008. IEEE 802.11 ad is developing a millimeter-wave (mmWave) based alternative physical layer (PHY) for the existing 802.15.3 Wireless Personal Area Network (WPAN) Standard e.g., IEEE 802.15.3-2003. This mmWave WPAN may operate in a band including the 57-64 GHz unlicensed band defined by FCC 47 CFR 15.255 and other regulatory bodies and may be referred to as “60 GHz”. The millimeter-wave WPAN may allow very high data rate (e.g., over 2 Gigabit per second (Gbps)) applications such as high speed Internet access, streaming content download (e.g., video on demand, high-definition television (HDTV), home theater, etc.), real time streaming and wireless data bus for cable replacement.
However, a mmWave communication link is significantly less robust than links operating at lower frequencies (e.g. 2.4 GHz and 5 GHz bands) due to the Friis transmission equation, oxygen absorption and high attenuation through obstructions. In addition, the mmWave communication link may use a directional antenna and/or antennas array to increase the communication range an operational rate. The use of a directional antenna makes a link very sensitive to mobility. For example, a slight change in the orientation of the device or the movement of a nearby object and/or person may disrupt the link.
In the IEEE 802.11 specification, the carrier sense mechanism solves the frame interference problem by not sending the frame in the presence of the carrier. The IEEE 802.11 assumption of equal (omni) carrier sense on any of the devices is very basic for CSMA/CA based WLAN and the physical carrier sense is an important mechanism of the multiple access.
This assumption of omni carrier sense is not valid in the 60 GHz spectrum. A communication link operating at mmWave frequencies (e.g., 60 GHz) has significant attenuation. In order to satisfy the link budget requirement, directional antennas may be used. One result of the massive use of the direct or directed antennas is that the carrier sense indication may not be equal at the transmitter and at the receiver. For example, a station may not sense the physical and virtual carrier of the frame transmitted by another station. Additionally, a station, may not sense the physical and virtual carrier of two interconnecting stations.
One notable disadvantage of WPAN 60 GHz network is that interference may occur when the same channel is used by two neighboring networks and an overlapping channel time for transmission is allocated to stations of both networks (e.g., a channel time allocation (CTA)).
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